This invention relates to an induction system for an internal combustion engine and more particularly to an improved control valve arrangement for an engine intake control system.
It has been known that the performance of an engine and particularly its power output can be substantially increased by employing multiple intake valves. Therefore, it is a common practice with many engines, particularly of the automotive type, to employ two intake valves per cylinder. However, the advantages of employing even more, and specifically three intake valves for each cylinder, are becoming recognized.
Although the use of multiple intake valves can be effective in increasing the power output of an engine, the use of such free-breathing induction systems can deteriorate the performance at low speeds and mid-range. The reason for this is that the intake charge flows relatively slowly into the combustion chambers under these conditions with the free-breathing intake passages. As a result, there is low turbulence in the combustion chamber and flame propagation under these low speed, low load conditions deteriorates.
In order to further improve the performance of three valve per cylinder engines, particularly under low speed running, it has been proposed to employe various tuning devices for the induction system. Although these tuning devices can improve volumetric efficiency, they still may not totally solve the problems under all conditions.
It is, therefore, a principal object of this invention to provide an improved control valve arrangement for a multi-valve engine wherein the control valve can be employed to generate turbulence in the combustion chamber without restricting the output at high-load and high-speed conditions.
It is a further object of this invention to provide an improved control valve assembly for a multi-valve engine wherein the desired types of turbulence can be generated in the combustion chamber under varying running conditions.
It has also been acknowledged that turbulence in the combustion chamber is effective under some running conditions so as to improve engine performance. Turbulence helps to increase the rate of flame propagation and ensures complete burning. However, the type of turbulence which is generated can be significant in controlling and improving engine performance. One type of turbulence, called "swirl," is by a rotary motion around the cylinder bore axis. This type of turbulence is relatively easy to generate, particularly with three-valve-per-cylinder engines. However, a different type of turbulence known as tumble has been found to give better performance under some running conditions. Tumble is a type of swirling motion, but the motion occurs about an axis that extends generally transversely to the cylinder bore axis. This type of motion is more difficult to generate, particularly with three-valve-per-cylinder engines.
It is, therefore, a still further object of this invention to provide an improved three-intake-valve-per-cylinder engine having a control valve that is usable to generate tumble in the combustion chamber under some running conditions.